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United States Patent |
5,105,685
|
Yoshida
|
April 21, 1992
|
Oil-sealing structure of motor
Abstract
An oil-sealing structure of a motor including a bearing supporting a motor
shaft, and an oil seal provided in the space between the motor shaft and a
bracket and positioned close to one end of the motor shaft while separated
by a predetermined distance from the bearing. An outer peripheral surface
of the motor shaft faces, within the space, an inner peripheral surface of
the bracket. Steps are formed on the motor-shaft outer peripheral surface
and positioned between the bearing and the oil seal, with their diameter
increasing in a stepped manner toward the bearing. A stepped groove is
formed on the bracket inner peripheral surface and positioned between the
bearing and the oil seal, with its diameter decreasing in a stepped manner
toward the bearing. An oil outlet is also formed on the bracket inner
peripheral surface for discharging oil which has penetrated beyond the oil
seal. The structure is capable of highly secure prevention of oil
penetration into the motor.
Inventors:
|
Yoshida; Yasushi (Kiryu, JP)
|
Assignee:
|
Mitsuba Electric Manufacturing Co., Ltd. (JP)
|
Appl. No.:
|
534868 |
Filed:
|
June 8, 1990 |
Current U.S. Class: |
74/606R; 74/6; 74/607 |
Intern'l Class: |
F16H 057/02; F02N 011/00 |
Field of Search: |
74/606 R,607,6,7 E
|
References Cited
U.S. Patent Documents
4726254 | Feb., 1988 | Kubo et al. | 74/606.
|
4763538 | Aug., 1988 | Fujita et al. | 74/6.
|
4867008 | Sep., 1989 | Yamaoka et al. | 74/606.
|
4907470 | Mar., 1990 | Kasemeier et al. | 74/606.
|
4938084 | Jul., 1990 | Morishita et al. | 74/6.
|
Primary Examiner: Luong; Vinh T.
Attorney, Agent or Firm: Oliff & Berridge
Claims
What is claimed is:
1. A combination of an oil-sealing structure of a motor having a motor
shaft, a bracket, a bearing provided in the space between said motor shaft
and said bracket to support said motor shaft, and an oil seal provided in
said space and disposed at a position close to one end of said motor shaft
and separated by a predetermined distance from said bearing, said
combination comprising:
an outer peripheral surface of said motor shaft and an inner peripheral
surface of said bracket which face each other within said space for said
predetermined distance between said bearing and said oil seal;
first steps formed on said outer peripheral surface of said motor shaft at
a position between said bearing and said oil seal, the diameter of said
steps increasing in a stepped manner toward said bearing; and
second steps formed on said inner peripheral surface of said bracket at a
position between said bearing and said oil seal, the diameter of said
second steps decreasing in a stepped manner toward said bearing to a
diameter smaller than the diameter of said bearing.
2. An oil-sealing structure as claimed in claim 1, further comprising an
oil outlet channel formed on said inner peripheral surface of said bracket
for discharging oil which has penetrated beyond said oil seal.
3. An oil-sealing structure as claimed in claim 1, wherein said oil seal is
in sliding contact with said shaft.
4. An oil-sealing structure as claimed in claim 1, wherein each of said
first and second steps comprise at least two stepped surfaces.
5. An oil-sealing structure according to claim 1, further comprising:
an annular oil stopper disposed around said shaft, said stopper forming a
step of increased diameter on said outer peripheral surface of said shaft.
6. A rotatable shaft and bearing assembly wherein the bearing is mounted in
a retaining means and said shaft extends through said bearing and
retaining means so as to be rotatably supported thereby, said assembly
having an oil-sealing structure comprising:
an oil seal mounted in said retaining means spaced apart from said bearing
along said shaft;
a stepped outer peripheral surface of said shaft positioned between said
bearing and said oil seal, the diameter of said shaft increasing in a
stepped manner toward said bearing; and
a stepped inner peripheral surface of said retaining means having a
plurality of steps positioned between said bearing and said oil seal and
spaced outwardly from said outer peripheral surface, an inner diameter of
said retaining means decreasing in a stepped manner toward said bearing to
a diameter less than the diameter of said bearing.
7. An assembly as claimed in claim 6, wherein said oil seal is in sliding
contact with said shaft.
8. An assembly as claimed in claim 6, further comprising an oil outlet
channel formed on said inner peripheral surface of said retaining means
for discharging oil which has penetrated said oil seal.
9. A rotatable shaft and bearing assembly wherein the bearing is mounted in
a retaining means and said shaft extends through said bearing and
retaining means so as to be rotatably supported thereby, said assembly
having an oil-sealing structure comprising:
an oil seal mounted in said retaining means spaced apart from said bearing
along said shaft; and
a stepped inner peripheral surface of said retaining means having at least
two steps positioned between said bearing and said oil seal and spaced
outwardly from an outer peripheral surface of said shaft, an inner
diameter of said retaining means decreasing in a stepped manner toward
said bearing, whereby oil which has penetrated said oil seal and has been
splayed outwardly from said shaft is prevented from reaching said bearing
by being driven away from said bearing and up said stepped surface by
centrifugal force.
10. An assembly as claimed in claim 9, further comprising an oil outlet
channel formed on said inner peripheral surface of said retaining means
for discharging said oil which has been splayed outwardly from said shaft.
11. An oil-sealing structure, comprising:
a rotatable shaft;
a bearing rotatably supporting said shaft;
an oil seal surrounding said shaft; and
a bracket supporting said bearing and said oil seal having
a bearing receiving portion, for receiving said bearing;
an oil seal receiving portion, for receiving said oil seal; and
an annular groove with first and second ends extending between said bearing
receiving portion and said oil seal receiving portion, said first end
being adjacent said oil seal receiving portion and said second end being
adjacent said bearing receiving portion,
said first end of said annular groove having a smaller diameter than said
oil seal receiving portion, said second end of said annular groove having
a smaller diameter than said bearing receiving portion, and said second
end having a smaller diameter than said first end,
wherein said shaft extends through said bearing and said oil seal.
12. An oil-sealing structure according to claim 11, wherein said annular
groove has a plurality of stepped surfaces.
13. An oil-sealing structure according to claim 11, wherein said annular
groove has three stepped surfaces.
14. An oil-sealing structure according to claim 11, wherein said shaft has
an annular recess with a reduced diameter located between said oil seal
and said bearing.
15. An oil-sealing structure according to claim 14, wherein said annular
recess is located adjacent said oil seal.
16. An oil-sealing structure according to claim 11, further comprising:
an annular oil stopper having first and second ends disposed around said
shaft between said oil seal and said bearing.
17. An oil-sealing structure according to claim 16, wherein said first end
of said oil stopper provides a stepped surface and said oil stopper
provides an increased diameter for said shaft adjacent said bearing.
18. An oil-sealing structure according to claim 16, wherein said second end
of said oil stopper is flared toward said second end of said annular
groove.
19. An oil-sealing structure according to claim 11, wherein said shaft is
slidably coupled to said oil seal.
20. An oil-sealing structure according to claim 11, further comprising an
oil outlet channel formed adjacent said first end of said annular groove
for discharging oil.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an oil-sealing structure of a motor for,
e.g., electrical equipment of a vehicle.
2. Description of the Prior Art
A motor of the above-mentioned type is generally such that the motor shaft
is dipped in pump oil, as in the case of a motor connected with a pump for
actuating an anti-lock brake (ALB) system. The inside of such a motor must
be protected from penetration of oil. For this purpose, as shown in FIG.
3, a double oil-sealing structure is adapted, in which, in addition to an
oil seal, an oil stopper is provided. However, this structure is still
insufficient because is fails to block a small amount of oil which
inevitably penetrates into the motor by flowing along the motor shaft.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, the present invention has
been accomplished in order to provide an oil sealing structure of a motor
which is capable of eliminating the above-described problem.
According to one aspect of the present invention, there is provided an
oil-sealing structure of a motor having a motor shaft, a bracket, a
bearing provided in the space between the motor shaft and the bracket to
support the motor shaft, and an oil seal provided in the space and
disposed at a position close to one end of the motor shaft and separated
by a predetermined distance from the bearing. The oil-sealing structure
comprises:
an outer peripheral surface of the motor shaft and an inner peripheral
surface of the bracket which face each other within the space; first steps
formed on the outer peripheral surface of the motor shaft at a position
between the bearing and the oil seal, the diameter of the steps increasing
in a stepped manner toward the bearing; second steps formed in the inner
peripheral surface of the bracket and at a position between the bearing
and the oil seal, the diameter of the second steps decreasing in a stepped
manner toward the bearing; and an oil outlet channel formed on the inner
peripheral surface of the bracket for discharging oil which has penetrated
beyond the oil seal.
According to the present invention, the above-specified structure is
capable of highly secure prevention of oil penetration to the inside of
the motor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional side view of a motor, showing one embodiment of an
oil-sealing structure according to the present invention;
FIG. 2 is an enlarged sectional view of essential parts of the structure;
and
FIG. 3 is a view corresponding to FIG. 2, showing a conventional
oil-sealing structure of a motor.
DESCRIPTION OF THE PREFERRED EMBODIMENT
One embodiment of the present invention will now be described with
reference to the drawings.
Referring to FIG. 1, reference numeral 1 denotes a motor for driving a pump
which actuates an ALB system. The motor 1 includes, as has been
conventionally known, a motor yoke 2, a permanent magnet 3, a rotor 4, a
motor shaft 5, a commutator 6, and a brush 7.
The motor shaft 5 is rotatably supported by bearings 9 which are mounted on
the motor yoke 2 and an end bracket 8 integrally assembled onto the yoke
2. One end 5a of the motor shaft 5 projects through the end bracket 8, and
a crank shaft 10 is eccentrically connected to this end 5a. The crank
shaft 10 is also connected, through a bearing 11, to a connecting rod 13
of a piston 12. Members, such as these, which constitute a pump section P
are accommodated in a pump yoke 14. The pump yoke 14 is assembled onto
that side of the end bracket 8 which faces the pump section P. The
interior of the pump yoke 14 is filled with brake oil.
Referring to FIG. 2, an inner peripheral surface of the end bracket 8,
across which the motor shaft 5 extends, is formed with a portion 9a
receiving the bearing 9, as well as a portion 15a receiving an oil seal
15. The receiving portion 9a is on the side of the inner peripheral
surface which is close to the motor 1, while the receiving portion 15a is
separated from the portion 9a by a predetermined distance, and is on the
side close to the pump section P. The oil seal 15, of which the inner
periphery is in sliding contact with the motor shaft 5, is fitted in the
receiving portion 15a. Between the bearing 9 and the oil seal 15, a part
of the inner peripheral surface of the end bracket 8 faces an outer
peripheral surface of the motor shaft 5. The end-bracket inner peripheral
surface has second steps 16, specifically, first stepped portion 16a,
second stepped portion 16b, and third stepped portion 16c, formed thereon,
the diameter of the portions 16a, 16b and 16 c decreasing in a stepped
manner toward the bearing 9. The stepped portions 16 constitute a stepped
annular groove 17 around the motor shaft 5. The end bracket 8 is also
formed with an oil outlet channel 18 which extends downward, as viewed in
FIG. 2, communicating the annular groove 17 with an oil tank, not shown,
disposed outside the end bracket 8.
On the other hand, the outer peripheral surface of the motor shaft 5 which
faces the above-described inner peripheral surface of the end bracket 8
has a recess 5b formed thereon positioned close to the oil seal 15. A
cylindrical oil stopper 19 is fitted on the motor shaft 5 and positioned
slightly distant from the recess 5b. The oil stopper 19 has a
funnel-shaped peripheral edge 19a which is on the side close to the
bearing 9, the edge 19a diverging toward the bearing 9. Thus, on the outer
peripheral surface of the motor shaft 5, first steps 20 are defined by the
recess 5b of shaft 5, the periphery of the intermediate portion 5c of
shaft 5 and the periphery of oil stopper 19. Therefore, the rising inner
wall of the recess 5b on the side close to the bearing 9, the end face 19b
of the oil stopper 19 on the side close to the oil seal 15 which forms a
step rising from the shaft 5, and the diverging peripheral edge 19a of the
stopper 19 together form first steps 20 which make the outer peripheral
surface of the motor shaft beyond the oil seal 15 increase in diameter
toward the bearing 9.
In the embodiment of the present invention having the above-described
construction, the inside of the pump yoke 14 and the inside of the motor 1
are sealed from each other by the oil seal 15 provided in the end bracket
8. However, a small amount of oil may enter the inside of the motor 1 by
flowing along the motor shaft 5. In such cases, with the oil-sealing
structure of the invention, the oil which has entered is prevented from
reaching the bearing 9 by the recess 5b formed on the motor shaft 5 and
the oil stopper 19 fitted thereon. The oil is further subjected to
centrifugal force generated by the rotation of the motor shaft 5,
whereupon the oil is splayed radially outward to be received in the
stepped annular groove 17 formed in the end bracket 8. Thereafter, the oil
within the groove 17 is returned therefrom to the oil tank through the
outlet channel 18.
In this way, according to the present invention, when a part of the oil in
the pump section P has entered beyond the oil seal 15, the oil-sealing
structure provides the following function. The oil which has entered is
blocked, first by the rising inner wall of the recess 5b on the side of
the bearing 9, and then by the end face of the oil stopper 19 on the side
of the oil seal 15. Even when a small portion of the oil flows inward over
the oil stopper 19, the peripheral edge 19a located on the side of the
bearing 9 prevents further inward advancement. In brief, an outer
peripheral surface of the motor shaft 5 which is formed by the
above-described members has its diameter increasing in a stepped manner
toward the bearing 9, thereby effectively preventing inward penetration of
oil. The oil thus prevented from penetration and maintained on the outer
peripheral surface of the motor shaft 5 is splayed by centrifugal force
caused by the rotation of the motor shaft 5 toward the annular groove 17
on the inner peripheral surface of the end bracket 8, to be received in
the groove 17. Since the annular groove 17 is stepped and has its diameter
decreasing in a stepped manner toward the bearing 9, the oil blown is
positively received by the stepped surfaces of the first to third stepped
portions 16 whose diameters decrease in a stepped manner. As a result, the
amount of oil present on the inner peripheral surface of the end bracket 8
is decreased toward the bearing 9 until there is substantially no oil in
the end. In brief, the inner peripheral surface of the end bracket 8
serves, in cooperation with the outer peripheral surface of the motor
shaft 5, to enable highly secure prevention of oil penetration to the
inside of the motor 1, thereby rendering the motor 1 free of oil adhered
to the commutator 6, the brush 7, etc., hence, rendering it capable of
exhibiting high reliability. The oil received in the annular groove 17 is
discharged to the outside of the end bracket 8 by flowing through the
channel 18. Accordingly, there is no risk that oil may remain in the end
bracket 8. Another advantage is that it is possible to detect, from the
amount of oil discharged, any damage or the degree of wear of the oil seal
15.
To summarize, the present invention has the following advantageous
features.
Even when oil has entered beyond the oil seal, heading toward the bearing,
the plurality of steps formed on the outer peripheral surface of the motor
shaft, with diameters increasing in a stepped manner toward the bearing,
serve to block the oil a number of times and securely.
When the oil is splayed toward the inner peripheral surface of the bracket
by centrifugal force generated by the motor shaft rotation, the stepped
annular groove having its diameter decreasing in a stepped manner toward
the bearing causes the oil to be received by the plurality of stepped
surfaces of the groove a number of the times, so that the oil amount
decreases toward the bearing until there is substantially no oil in the
end. Thus, highly secure prevention of oil penetration into the motor is
possible, thereby rendering the inside of the motor free from oil adhesion
to various members, hence, rendering the motor highly reliable.
The oil in the groove is discharged to the outside of the bracket through
the oil outlet channel. This is advantageous in that oil is prevented from
remaining in the bracket, and that any breakage or the degree of wear of
the oil seal can be detected from the amount of discharged oil.
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